Torque transmitting and/or energy absorbing device



y 1965 E. w. REINSCH 3,184,009

TORQUE TRANSMITTING AND/OR ENERGY ABSORBING DEVICE Filed Aug. 16, 1962INVENTOR.

' Earl W. Reinsch y zm is A homey I l i United This invention relates toa torque transmitting and/ or energy absorbing device and isspecifically directed to brakes, clutches and the like.

More particularly, the invention is directed to the combination of asintered ferrous brake lining or facing used in conjunction with a brakemember formed from iron substantially free from ferrite and wherein anygraphite present is in nodular or spheroidal form.

- An object of the invention is to produce a combination of elements foruse in a torque transmitting and/ or an energy absorbing device andparticularly a brake wherein the uniformity of operation is improved.

In carrying out the above object it is a further object of the inventionto reduce cold pedal effect normally present in automotive brakingsystems.

Further objects and advantages of the present invention Will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIG. 1 is a photo micrograph of a cross section of a conventional castiron drum as commonly used in automotive vehicles showing the conditionof the graphite therein, and

FIG. 2 is a photo micrograph of a cross section of a nodular iron drumwherein the percentage of graphite is substantially the same as thepercentage in FIG. 1 and wherein the graphite is in the spheroidizedcondition.

Recent trends in automotive design and improved road conditions havemade possible higher speed travel in automotive vehicles. These trendshave required improvement in brake design and construction so that thevehicles may be stopped within a safe distance even from the higherspeeds. In order to make this condition possible, heavy duty brakelining materials have been developed which are metallic in nature andwhich will withstand the high temperature conditions which prevail inthe brake during a stop or stops from high speeds. These temperatureconditions are sufficient to, in many instances, cause charring ofnon-metallic type linings including organic type material. This newbrake lining material which is specifically a sintered ferrous materialincluding graphite, is disclosed in some detail in US. Patents 2,945,291and 2,945,929, among others, which are assigned to the assignee of thisapplication. These metallic friction materials have the ability toprovide reasonably constant coefficients of friction over a wide rangeof temperatures and specifically are capable of maintaining thereasonably high coefiicient of friction at high temperatures whereby thevehicle may be brought to a stop without excessive pedal pressure andwherein the friction material remains unharmed due to the rise intemperature.

These same materials, however, do not provide the ultimate in cold pedaloperation under normal conditions. Cold pedal may best be defined as areduction in effectiveness of the brakes after a period of inactivity,that is, when the automotive vehicle has been standing idle for a periodof time, for example, over night, the first stop or first few stops maderequire greater pedal pressure to bring the car to a stop than dosubsequent operations of the braking system. This condition, while notserious States Patent 3,184,009 Ce Patented May 18, 1965 from a safetypoint of view, is nevertheless, annoying and has acted as a deterrent insome cases, toward the application of metallic brake linings in pleasurevehicles.

I have found that cold pedal conditions may be greatly lessened byutilizing a specific combination of elements in the braking system.Thus, when using a ferrous metal brake lining such as is disclosed, forexample, in Patent 2,945,291, I have found that the cold pedal efiectsare greatly lessened if a nodular iron brake drum is used in combinationtherewith. Most automotive vehicles made today utilize gray cast ironbrake drums. The combination of the metallic lining with the nodulardrum reduce the cold pedal effect in the order of 25% whereby muchbetter and more uniform operation is obtained from the braking system.

The only explanation for this improvement that can be offered is thechange in shape of the dispersed graphite in the iron drum. When using agray cast iron drum, the gray iron has graphite dispersed through theferrous matrix in long strings or flakes. In the nodular iron drum thegraphite is in the form of nodules or spheres and apparently thisdifference in the physical form of the graphite tends to reduce theeffective area of graphite which has a marked effect on the cold pedalcondition.

A typical cold pedal test procedure is as follows: the linings and drumsare conditioned by making ten stops at /2 mile intervals each from 40miles per hour at a deceleration rate of 10 ft./sec. The vehicle is thenparked for a minimum of two hours. The cold pedal is then evaluated bymaking ten stops at half mile intervals from 40 miles per hour at adeceleration rate at 10 ft./sec. wherein the initial and final linepressures required to maintain the specific deceleration is recordedthrough each stop.

Using brake linings as disclosed in the aforementioned patent with astandard cast iron drum conditioning, the tenth stop of the schedulerequired 270 p.s.i. to produce the desired deceleration. After the carwas parked for the two hour rest period from a forward stop, the firstcheck stop after the cooling off period required an initial linepressure of 320 p.s.i., which may be termed the cold forwardeffectiveness. It the car was parked for the cooling off period from areverse stop, the first check stop required initial line pressure of 385p.s.i. This may be termed cold reverse effectiveness.

If the car is parked with a forward stop before the cooling period and acontrolled reverse stop is made before the first check stop, the firstcheck stop requires an initial line pressure of 385 p.s.i. This is alsocalled the cold reverse effectiveness.

It will be noted that the line pressure increase to effect a specificdeceleration to stop is the same to effect a stop if the immediateprevious stop was a reverse stop, Whether the reverse stop was before orafter the cooling off period.

Thus, the difference between warm brake effectiveness at 270 p.s.i. andcold reverse brake effectiveness at 385 p.s.i. is p.s.i. This differencewill be detected by the driver and is known as hardened pedal. It occursin normal driving when a driver backs out of a parking space and then isrequired to make a forward stop. The change in brake output is notedregardless of the car speed.

The same scheduled tests were made using nodular iron drums with allother conditions identical. In this instance the warm effectivenessdropped to 230 p.s.i., the cold forward effectiveness to 275 p.s.i. andthe cold reverse effectiveness to 300 p.s.i. Thus, the nodular iron drumnarrowed the difference between the warm stop and the cold reverse stopto 70 p.s.i. over the 115 p.s.i. required when using a gray cast irondrum.

In addition to the improved brake characteristics, nodular iron hasgreatly improved tensile strength over the usual gray cast iron. Oneuseful grade of nodular iron is SAE type 2 806003 which has a tensilestrength in the order of 80,000 p.s.i. as compared to 30,000 p.s.i. forgray cast iron. Other grades of nodular iron are also useful providingthat the iron has a matrix substantially free from ferrite. This is avery important consideration since free ferrite produces scoringtendencies and is not useful in braking applications.

Nodular iron offers another benefit that is commercially important,namely, due to the increased strength over gray cast iron, the drums maybe madeconsiderably lighter with decreased wall thickness Withoutsacrificing ruggedness. Further, the increased strength permits integralcasting of the drum with the front wheel hub which reduces costs whileyielding improved braking operations.

In place of nodular iron, malleable iron is also useful providing it hassubstantially the same metallographic structure as the nodular iron andis within the same tensile strength range. Such malleable iron has thegraphite in spheroidal form much as it occurs in nodular iron and issubstantially free from ferrite and approaches nodular iron for thepurpose at hand.

In'general, sintered ferrous linings and/ or facings having a sinteredferrous base and including graphite in quantities above 10% with orWithout well known friction fortifying and/ or modifying materials, maybe used effectively in the combination.

In general, a drum having a nodular graphitic structure when used incombination with a sintered, ferrous brake lining material will offerimproved operational characteristics, particularly in the cold pedalrange. Such improvements are easily noticeable by the operator of theand/ or other torque transmitting and/or energy absorbs.

ing'devices wherein sliding or rubbing engagement occurs between theseveral elements of the structure.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A brake for use in an automotive vehicle and the like, comprising incombination; a sintered ferrous brake. lining and a braking surfacecooperating with said lining,

said braking surface consisting of nodular iron.

2. A brake for use in an automotive vehicle and the like comprising incombination; a sintered ferrous brake lining and a brake drum for use asa rubbing surface M against said lining, said drum having its'contacting surface consisting of nodular iron.

References Cited by the Examiner UNITED STATES PATENTS 1,881,097 lO/32Sargent. 1,900,804

ARTHUR L. LA POINT, Primary Examiner. EUGENE G. BOTZ, Examiner.

3/33 Crowe 188-218 2,945,291 7/60 Ankeny 29 1s2.3,

1. A BRAKE FOR USE IN AN AUTOMOTIVE VEHICLE AND THE LIKE, COMPRISING INCOMBINATION; A SINTERED FERROUS BRAKE LINING AND A BRAKING SURFACECOOPERATING WITH SAID LINING, SAID BRAKING SURFACE CONSISTING OF NODULARIRON.